1. Field of the Invention
The present invention relates to a high frequency dielectric ceramic composition for use in a high frequency region such as microwave and millimeter-wave regions, a dielectric resonator, a dielectric filter, a dielectric duplexer, and a communication device each using the high frequency dielectric ceramic composition.
2. Description of the Related Art
Heretofore, dielectric ceramics have been widely used for dielectric resonators, circuit substrate materials, and so forth which operate in a high frequency region such as microwave and millimeter-wave regions.
The dielectric characteristics required for the high frequency dielectric ceramics are as follows. (1) The wavelength of an electromagnetic wave is reduced to 1/(∈r)1/2 in a dielectric. Accordingly, to meet requests for the reduction in size of the ceramics, it is required for the dielectric constants (∈r) to be large. (2) The dielectric losses should be low, i.e., the Q values should be high. (3) The stability of the resonance frequencies for temperature should be high, i.e., the temperature coefficients (τf) of the resonance frequencies should be near 0 (ppm/° C.).
Heretofore, as the above-described dielectric ceramics, Re2O3—Al2O3—SrO—TiO2 (Re: rare earth element) type materials, and the materials containing Mn added thereto are disclosed, e.g., in Japanese Unexamined Patent Application Publication No. 11-71171 and Japanese Unexamined Patent Application Publication No. 2000-203934.
The Re2O3—Al2O3—SrO—TiO2 type materials of the related art are superior in that the dielectric constants (∈r) are high, the Q values are high, and the temperature coefficient (τf) of the resonance frequency can be controlled to be near zero. However, with recent advancement of the communication enterprises, high frequency electronic parts have been required to have higher qualities. Moreover, materials for dielectric ceramics have been required to have a higher Q value than the related art materials.